1. Technical Field
The present disclosure relates to a structure for preventing freezing of a blow-by gas in an intake manifold, which is capable of preventing moisture contents in the blow-by gas introduced into the manifold from freezing even under a low temperature environment.
2. Related Art
Generally, an intake manifold is provided in a vehicle to uniformly distribute air or a mixed gas to cylinders of an engine. The intake manifold includes a plenum chamber configured to temporarily store a mixed gas supplied to a lower side thereof, a throttle body disposed to communicate with one side of the plenum chamber to allow the mixed gas that passes through a carburetor to flow, an intake runner configured to guide the mixed gas stored in the plenum chamber to flow into each cylinder, and the like.
In the mixed gas supplied to each cylinder through the intake runner, a gas discharged from a cylinder head of the engine through a gap between a cylinder and a piston during a compression stroke and an expansion stroke is referred to as a blow-by gas. The blow-by gas is discharged from the cylinder head of the engine, passes through a discharge passage of a cylinder block and a head cover of the cylinder head through a positive crankcase ventilation (PCV) system, and then is recycled to the intake manifold through a separate PCV hose.
The PCV hose is connected to a PCV nipple installed in a surge tank, the blow-by gas is introduced into a PCV chamber through the PCV nipple, and the blow-by gas introduced into the PCV chamber is discharged to the plenum chamber and is subsequently mixed with a newly supplied mixed gas and distributed to each intake runner.
Under a condition in which the ambient temperature is below a freezing temperature of water as in cold regions or during a winter season, while moisture contained in the blow-by gas is introduced into an intake side, a freezing phenomenon, in which condensed water freezes in a passage or the like of the PCV nipple, occurs due to a temperature difference with the outside air. When such a freezing phenomenon occurs, the PCV nipple is clogged and fail to operate normally. Thus, the blow-by gas may not be discharged from the inside of the engine to the surge tank and may be blocked. As a result, the blow-by gas increases pressure inside the engine to adversely affect engine sealing, resulting in leakage at a sealing joint.